Definition

It is the infection of the endocardium (inner layer), mainly the lining of the chamber or heart valve or congenital anomaly.
It usually occurs at the site of pre-existing heart disease or septal defect. Infection with virulent organisms may cause acute endocarditis in the normal heart (e.g. Staphylococcus aureus).

Acute Endocarditis

Causes

Usually by highly virulent and invasive organism, e.g. S. aureus, Streptococcus, Pneumococcus.
It can affect damaged as well as normal heart. Vegetations are usually very large and valve destruction is more than in subacute endocarditis.

Clinical Features

Symptoms

• Fever, usually very high with chill and rigor.
• Headache, bodyache, malaise, weakness.
• Chest pain, breathlessness.

Signs

• Patient looks toxic with very high-temperature.
• Prominent and changing heart murmur.
• Stigmata of subacute or chronic endocarditis are usually absent.
Subacute Bacterial Endocarditis (SBE) usually caused by organisms of low-virulence, affecting rheumatic or congenitally abnormal
valves.

Predisposing Factors or Causes of Subacute Bacterial Endocarditis (SBE)

• Rheumatic valve lesion (e.g. AR, MR).
• Congenital heart disease (VSD, PDA, bicuspid aortic valve, coarctation of aorta, TOF).
• Prosthetic valve.
• Dental extraction.
• Instrumentation (IV canula, CV line, cardiac catheterization).
• Cardiac surgery.
• IV drug abuse (right sided endocarditis is more common, especially tricuspid valve).

Organisms Causing Infective Endocarditis

1. Subacute bacterial endocarditis—
–– Strep. viridans—mo st common (35–50%).
–– Enterococcus faecalis, Enterococcus faecium.
–– S. bovis (associated with large bowel carcinoma), S. milleri and other streptococci.
–– Staphylococcus aureus or epidermidis.
–– HACEK organisms (Haemophilus, Actinobacillus, Cardiobacterium hominis, Eikenella, Kingella).

2. Acute bacterial endocarditis—
–– S. aureus (most common).
–– Others—Pseudomonas, Candida, Streptococcus pneumonae, Neisseria gonorrhoea.

3. Postoperative endocarditis—
–– Staphylococcus albus.
–– Candida.
–– Aspergillus.
–– All other organisms causing subacute and acute endocarditis.

Clinical Features

Symptoms

• Fever, usually low-grade continuous which is persistent and does not respond to usual antibiotics.
• Chest pain and palpitation.
• Difficulty in breathing .
• Anorexia, weight loss, malaise, weakness, night sweat, arthralgia.
• Symptoms of embolism according to involvement like brain (CVD), kidney (renal infarction),
lung (pulmonary infarction).

Signs

General Examination—

1. Appearance—Ill looking, emaciated and toxic, anaemia.
2. In hands—
–– Clubbing involving all the fingers and toes.
–– Osler’s node (small painful violaceous raised nodule, present on the tip of the fingers).
–– Janeway lesion (large painless erythematous macules on the palm and sole).
–– Infarction at the tip of fingers or toes, petechiae on the dorsum or other parts.
–– Splinter haemorrage (subungual).
–– Infarction due to embolism.
3. Pulse—tachycardia.
4. BP may be low.
5. Precordium—
–– Signs of previous heart disease (AR, MR, ASD, VSD, PDA, etc.).
–– Murmur—appearance of new murmur or changing character of previous murmur.
6. Abdomen—splenomegaly may be present.
7. Fundoscopy—Roth’s spot (white-centered retinal haemorrhage).

Investigations

• CBC, ESR—anaemia, neutrophilic leucocytosis, high ESR.
• CRP—high.
• Blood culture (both aerobic and anaerobic)—3 samples from different sites at 1-hour apart.
• Echocardiography—to see vegetation, valvular lesion or congenital anomaly. Transoesophageal
echocardiography is more sensitive.
• Urine R/M/E (haematuria, proteinuria may be present).
• Chest X-ray shows cardiomegaly.
• ECG.
• Urea and creatinine.

Vegetation:

It is a small solid mass composed of platelet, fibrin and organism, occurring at the site of endothelial damage in the valve or endocardium. It may result in embolism.

Complications of SBE

• Heart failure (LVF is a common cause of death).
• Valve destruction, regurgitation, obstruction.
• Aortic root abscess.
• Systemic embolism.
• Right-sided endocarditis involves the pulmonary valve and may cause septic pulmonary emboli, occasionally infarction and lung abscess.

Causes of Culture Negative Endocarditis

• Prior antibiotic treatment (common cause).
• Fungal, yeast, anaerobic infection or Q fever.
• Right-sided endocarditis.
• Noninfective endocarditis: Libmann Sac’s (nonbacterial verrucous endocarditis in SLE), marantic endocarditis (nonbacterial thrombotic or verrucous endocarditis found in malignancy, such as bronchial carcinoma).

Treatment

Ideally antibiotic should be given according to culture and sensitivity. However, treatment should be started as soon as the blood sample is sent for culture and sensitivity.
• For viridans streptococci—Benzyl penicillin 1.2 g IV 4 hourly and gentamycin 1 mg/kg IV 8 hourly for 4 weeks or ceftriaxone 2 gm once daily IV for 4 weeks or vancomycin 15 mg/kg IV 12 hourly for 4 weeks.
• In acute case—flucloxacillin 2gm IV 6 hourly is added to cover staphylococci.
• In penicillin allergy or meticillin resistant Staph. aureus (MRSA) infection—triple therapy with vancomycin with gentamycin. Or another regimen—vancomycin 1 gm 12 hourly IV with ceftriaxone 2 g every 24 hours.
• In penicillin resistant case—Flucloxacillin plus gentamicin IV.
• In prosthetic valve endocarditis—IV penicillin 6 weeks and IV gentamicin 2 weeks should be given.
• For HACEK organisms—ceftriaxone 2 gm IV once daily for 4 weeks. If the prosthetic valve is involved, then treatment should be given for 6 weeks.
• Q fever endocarditis—prolong treatment with doxycycline and rifampicin or ciprofloxacin.

Prevention during Dental Procedure

Routine antibiotic prophylaxis prior to dental procedure is no longer recommended which is not proved to be effective. However, in few high-risk cases, antibiotic prophylaxis may be considered. These are—
• Prosthetic cardiac valve.
• Previous infective endocarditis.
• Congenital heart disease.

Drugs used for prophylaxis are—

• Amoxicillin 2 gm 1 hour before procedure.
• If penicillin allergy—clindamycin 600 mg or cephalexin 2 gm or azithromycin or clarithromycin 500 mg 1 hour before procedure.
• If the patient is unable to take by mouth, parenteral therapy may be given with ampicillin 2 gm IV or IM 30 minutes before the procedure. In penicillin allergy, clindamycin 600 mg IV 1 hour before the procedure or cefazolin 1 g IM or IV 30 minutes before procedure.

Indications of Cardiac Surgery

• Progressive heart failure from valve damage.
• Valvular obstruction.
• Repeated embolisation.
• Fungal endocarditis.
• Persistent bacteraemia in spite of adequate antibiotic therapy.
• Myocardial abscess.
• Endocarditis of prosthetic valve.
• Large vegetation in left-sided valve.